Plasticized monomeric adhesive compositions and articles prepared therefrom



United States Patent PLASTICIZED MONOMERIC ADHESIVE COMPO- SITIONS AND ARTICLES PREPARED THERE- FROM Frederick B. Joyner and Harry W. Coover, Jr., Kingsport,

Tenn., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application June 2, 1954, Serial No. 434,079

14 Claims. (Cl. 154- 43) This invention relates to monomeric tat-cyanoacrylate adhesive compositions containing dissolved therein an ester plasticizer suitable for preventing failure of the adhesive bond after aging, and to composite articles prepared using such adhesive compositions.

The monomeric tt-cyanoacrylate esters of the formula in which R represents an alkyl group of l-8 carbon atoms, a cyclohexyl group, or a phenyl group, find widespread utility as adhesive compositions for bonding a great variety of similar and dissimilar materials, including both porous and nonporous materials. Such u-cyanoacrylate esters are used in the monomeric form and allowed to autopolymerize in situ in a thin film between surfaces to be adhered together. The adhesive composition can include a single monomeric u-cyanoacrylate ester or a mixture of such esters. The use of a-cyanoacrylate adhesives broadly is described in the copending application of Harry W. Coover, Jr. and Newton H. Shearer, Jr. Serial No. 318,325, filed November 1, 1952. As described in that application, the monomeric adhesive compositions stabilized with sulfur dioxide or a mixture of sulfur dioxide and another polymerization inhibitor such as hydroquinone can be stored in bulk for prolonged periods of time without polymerization and still polymerize rapidly without the use of a polymerization catalyst or the application of heat or pressure when spread in a thin film on the surface to be bonded. Such adhesive compositions are unique in their ability to bond a great variety of materials including glass, metals, plastics, wood, textiles, paper, and similar materials in a high strength bond. The adhesive bonds which are obtained usually possess a very high degree of bond strength over prolonged periods of time. In some cases, however, pan ticularly after prolonged aging of bonded rigid elements, the bond can be fractured upon sudden shock. This 'occasional bond failure under shock is, of course, undesirable, since the adhesive bond is desirably subject to no failure in any case.

It is accordingly an object of this invention to provide improved ot-cyanoacrylate adhesive compositions containing a plasticizing material which is eflective to obvlate objectionable bond failure after aging.

Another object of the invention is to provide monomeric e-cyanoacrylate adhesive compositions containing dissolved therein a minor amount of an ester plasticizer which does not diminish the adhesive properties of the composition, but which is sufficient to plasticize the poly merized adhesive bond to a sufiicient degree to overcome the chance of failure of the adhesive bond under sudden shock.

Other objects will be apparent from the description and claims which follow.

These and other objects are attained by 'means of this invention wherein. adhesive compositions comprising monomeric tt-cyauoacrylate esters of the formula in which R is either an alkyl group of 1-8 carbon atoms, a cyclohexyl group, or a phenyl group, contain from l-2()% by weight, based on the weight of the monomeric ester, of at least one ester plasticizer of the type defined hereinafter. which is used in practicing the invention can be prepared in any desired manner. Thus, for example, these monomeric esters can be prepared by reacting a suitable ct-cyanoacetate with formaldehyde in aqueous or nonaqueous medium in the presence of a basic condensation catalyst to form a low molecular weight polymer which is thereafter depolymerized by heating under reduced pressure to give monomeric lat-cyanoacrylate suitable for use in practicing the invention. The preparation of typical a-CYZIHOHCIYlEti-f: esters is described in the copending applications of Coover and Shearer, Serial No. 318,325, filed November 1, 1952, and of Joyner and Hawkins, Serial No. 415,422, filed March 10, 1954 now U. S. 2,721,858. Any of such tic-cyanoacrylate monomers or mixtures thereof can be used in practiceing the invention.

In accordance with this invention, the monomeric adhesive composition contains dissolved therein from i-2O% by weight, and preferably from 1 to about 5% by weight, based on the weight of the cyanoacrylate ester, of one or more ester plasticizers of the following kinds. The ester plasticizer can be an alkyl ester of an aliphatic monocarboxylic acid of the formula RCOOR1 Z X in which R is an alkyl group of 1-17 carbon atoms, R1 is an alkyl group of l-8 carbon atoms, and X is either H, -CN, -Cl or -SO2R. The plasticizer can also be an alkyl ester of an aliphatic dicarboxylic acid of the formula R1OOC( CH2 n-COORi in which n is a Whole integer in the range of l-8 and R1 is an alkyl group of l-8 carbon atoms. Similarly, the alkyl phosphates in which each alkyl group contains 1-8 carbon atoms and the triaromatic phosphates such as triphenyl phosphate and tricresyl phosphate are suitably employed. The polyfunctional aliphatic esters such as the acyl triesters of glycerin in which each acyl group contains 2-18 carbon atoms are also suitably employed in practicing the invention. Other suitable plasticizers include the aliphatic and aromatic phosphonates, and particularly the dialkyl alkylphosphonates in which each alkyl group contains from 1-8 carbon atoms. Any of these esters can be used either alone or in combination in the compositions of this invention. We have found that such esters can be incorporated into the monomeric ccyanoacrylates'in' amounts of as much as 20% by weight, based on the monomerj weight, without affecting the adhesive action or strength of the adhesive bond to an ohvjectionabl-e degree. Amounts ofp'lasticizer above 20% by weight seriously retard the rapid adhesive action and The monomeric tit-cyanoacrylate.

hesive bonds which are obtained have excellent tensile strength and possess high resistance to shock even after. months of aging. The plasticizers serve the further purpose of fiexibilizing the adhesive bond to some extent, which is a particular advantage in certain applications such as the bonding of films and similar flexible elements.

It will be understood that any of the ester plasticizers as defined herein can be used in practicing the invention. Typical esters which are suitable include the alkyl esters of cyanoacetic acid such as methyl cyanoacetate, ethyl cyanoacetate, butyl cyanoacetate, hexyl cynnoacctate, and the like; succinate esters such as dimethyl succinatc, dicthyl succinate, dioctyl succinate, dibntyl succinate, and similar succinate esters wherein the a kyl groups con tain from 1-8 carbon atoms; sebacate esters wherein the alkyl groups contain from 1-8 carbon atoms, such as dimethyl sebacate, diethyl sebacate, dioctyl s ebacate, and the like; adipic acid esters such as dimethyl adipate, diethyl adipate, dioctyl adipate, and the like; phthalate esters such as dioctyl. phthalate, diethyl phthalate, and similar alkyl phthalates wherein the alkyl groups contain from 1 6 carbon atoms; acyl triesters of glycerin such as glyceryl triacetate, glyceryl tributyrate, glyceryl trilaurate, and similar acyl triesters in which the acyl group contains from 2-48 carbon atoms; alkyl esters of phosphoric acid providing such esters are free of acid and including such esters as triethyl phosphate or the like; aromatic phosphates such as triphenyl phosphate, tricres'yl phosphate, and the like; phosphonates such as diethyl ethylphosphonate, and the like; and similar ester plasiicizers as defined herein. Unexpectedly, these ester plasticizers could be used in amounts sufficient to flexibilize the polymerized adhesive bond without adversely affecting the desired degree of adhesion when employing the monomeric compositions.

The utility of the compositions embodying the invention is illustrated by the following examples.

Example 1 A similar laminated glass article bonded with unplasticized monomeric methyl tx-cyanoacrylate was allowed to age for four months. Upon severe tapping, a complete bond failure was observed. It is thus apparent that rigid articles such as laminated glass have a tendency to fracture in the adhesive bond when an unplasticized adhesive composition is employed and the laminated article is allowed to age. for a prolonged period.

Example 3 Two pieces of ordinary glass were bonded together using an adhesive composition consisting of methyl a-cyanoacrylate monomer containing 1% by weight of butyl cyanoacetate based on the weight of the cyanoacrylate monomer. This bonded article was allowed to stand for 25 days and then was tapped sharply until breakage occurred. Examination of the break showed that only 1% of the bonded area had broken, and the "remainder of the break was in the glass itself. It is thus apparent that by the use of as little as 1% of a suitable plmsticizer as described herein, the tendency of rigid laminated articles to faildue to fracture of the adhesive bond is largely overcome.

. Example 4 Laminated glass which had been bonded together by 4 r means of an adhesive composition of methyl a-cyanoaerylate monomer containing 1% by weight of butyl cyanoacetate was allowed to age for six months. At the end of this period, the bonded article was sharply tapped until breakage occurred. As in the previous example, the breakage occurred in the glass itself and no failure at the bondsurface was observed. Thus the plasticized compositions of this invention largely obviate the'possibility of bond failure due to ageing, and the action of the plasticizer in this respect is retained for prolonged periods of time. Y

- Example 5 Similar results are observed with any of the ester plasticizers as defined herein. .Thus, for example, two pieces of glass were bonded together by means of methyl e-cyanoacrylate monomer plasticized with 2% by weight of dimethyl succinate. After 25 days ageing, the bonded object was tapped until breakage occurred. In this case, bond failure was observed in only 8 to 10 percent of the bonded area as compared with a bond failure of in Example 1.

Example 6 A glass to glass bond was formed by polymerizing in situ monomeric methyl a-cyanoacrylate plasticized with 5% by weight of dimethyl sebacate. After two months ageing, no bond failure was observed when the laminated article was broken.

Example 7 The plasticizer can be used in amounts up to 20% by weight of plasticizer based on the weight of the monomeric cyanoacrylate. A glass to glass bond was formed from monomeric methyl u-cyanoacrylate containing 20% by weight of dioctyl adipate. This adhesive mixture was somewhat slowerin setting up than was the unplasticized methyl cyanoacrylate, but after four months ageing, the bond remained strong.

Example 8 As has been described, the compositions embodying this invention can be used for bonding a variety of materials. In a typical case, a metal to metal bond prepared by using monomeric ethyl a-cyanoacrylate plasticized by means of 5% by weight of butyl cyanoacetate showed no loss of tensile strength after three months ageing.

Example 9 Two pieces of glass were bonded together in the usual fashion using monomeric methy m-cyanoacrylate containing 3% by weight of methyl methylsulfonylacetate, CHsSOaCHaCOzCHs. The resulting bond had a high degree of tensile strength and good ageing characteristics.

- Example 10 Due to the flexibilizing action of the plasticizer on the adhesive bond, the compositions of this invention can be readily employed for bonding together flexible materials. Thus, for example, two pieces of polyterephthalate film were bonded together using methyl u-cyanoacrylate monomer plasticized by means of 2% by weight of dimethyl sebacate. The bond showed a high tensile strength and good flexibility after three months ageing.

Example 11 area-res T us msans this "ia s ifis fi y c he cyanoacrylate adhesive compositions is greatly increased. The possibility of bond failure upon ageing is minimized or obviated. The action of the plasticizer is effective to give flexible bonds which have added utility in the bonding of flexible articles wherein a rigid bond is undesirable. The compositions embodying this invention can be compounded. with any of, the materials which are ordinarily used in a-cyanoacrylate adhesive compositions. Thus, for example, the compositions usually contain at least 0.001% by weight based on theweight of the monomeric material of a suitable acidic polymerization inhibitor which prevents the polymerization of the adhesive composition in bulk during storage. The adhesive compositions of this invention desirably contain a gaseous polymerization inhibitor dissolved therein and preferably sulfur dioxide in an amount of about 0.001 to 0.003% by weight. In this range of concentrations, the polymerization inhibitor is eflfective during shelf storage in bulk but does not prevent autopolymerization of the adhesive composition when it is spread in a thin film on the surface to be bonded. Such inhibited compositions do not require the use of heat, pressure or polymerization catalyst during use. If larger amounts of polymerization inhibitor are used, the adhesive action can be speeded up by the use of heat or pressure or a basic polymerization catalyst if desired, and in the case of the higher esters of cx-cyanoacrylic acid such polymerization adjuncts may be desirable in some cases. The adhesive compositions can contain any of the other compounding ingredients which are normally employed such as "iscosity modifiers, coloring agents, fillers, pigments, and the like.

Although the lower alkyl esters of a-cyanoacrylic acid are desirably employed in practicing the invention, any of the other esters as defined herein can be used as well as combinations of two or more of such esters. Similarly, the plasticizer is usually a single material for convenience, but mixtures of two or more of the plasticizers can be used if desired.

The invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be eifected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A composite article comprising at least two elements adhered together by an in situ polymerized layer of an adhesive composition comprising monomeric acyanoacrylate ester of the formula CHa=C-CO OR wherein R is from the group consisting of alkyl groups of 1-8 carbon atoms, cyclohexyl groups and phenyl groups, and 1-20% by weight based on the weight of said a-cyanoacrylate ester of at least one ester plasticizer selected from the group consisting of alkyl esters of aliphatic monocarboxylic acids of the formula Iii-0001M X wherein R is an alkyl group of 1-17 carbon atoms, R1 is an alkyl group of 1-8 carbon atoms, and X is a member of the group consisting of H, CN, Cl and --SO2R, alkyl esters of aliphatic dicarboxylic acids of the formula wherein n is a whole integer of from 1 to 8, and R1 is an alkyl group of 1-8 carbon atoms, trialkyl phosphates wherein each alkyl group contains l-8 carbon atoms, triaromatic phosphates selected from the group consisting of triphenyl phosphate and tricresyl phosphate, acyl 8 triesters of gly cerine wherein each acyl mupg'centa as 2-18 carbon atoms, dialkyl alkyl phosphonates wherein each-alkyl group contains 1-8 carbon atoms, "and'alkyl phthalates wherein each alkyl group contains l-8 carbon atoms.

2'. A composite article comprising at least two rigid element-s adhered togetherbby an in situ polymerized layer of an adhesive composition comprising monomeric alkyl a-eyanoacrylate wherein the alkyl group contains 1:8 carbon atoms, and 1-20% by weight based on the weight of said u-cyanoacrylate of plasticizer comprising an alkyl ester of an aliphatic monocar'boxylic' acid, said acid containing l-l8 carbon atoms and said alkyl group containing 1-8 carbon atoms.

3. A composite article comprising at least two rigid elements adheredtogether by an in situ polymerized layer of an adhesivelcornposition comprising monomeric alkyl a-cyanoacrylate wherein the alkyl group contains 11-8 carbon atoms and 11-20% by weight, based on the weight of a-cyanoacrylate, of alkyl a-cyanoacetate wherein the alkyl group contains 1-8 carbon atoms.

4.. A composite. article. comprising at least two. rigid elements adhered together by an in situ polymerized layer of an adhesive composition comprising monomeric alkyl .s yanoa rylate wherein the alkyl group contains 1-8 carbon atoms and 1-20% by weight, based on the weight of a-cyanoacrylate, of alkyl diester of a polymethylene dicarboxylic acid, said dicarboxylic acid containing 1-8 carbon atoms and each of said alkyl groups containing 1-8 carbon atoms.

5. A composite article comprising at least two rigid elements adhered together by an in situ polymerized layer of an adhesive composition comprising monomeric alkyl a-cyanoacrylate wherein the alkyl group contains 1-8 carbon atoms, and 1-20% by weight based on the weight of said a-cyanoacrylate of tricresyl phosphate.

6. A composite article comprising at least two rigid elements adhered together by an in situ polymerized layer of an adhesive composition comprising monomeric alkyl Ill-000111 X wherein R is an alkyl group of 1-17 carbon atoms, R1 is an alkyl group of l-8 carbon atoms, and X is a member of the group consisting of -H, CN, Cl and -SO2R, alkyl esters of aliphatic dicarboxylic acids of the formula RIOOC(CHZ)n-COOR wherein n is a whole integer of from 1 to 8, and R1 is an alkyl group of l-8 carbon atoms, trialkyl phosphates wherein each alkyl group contains 1-8 carbon atoms, triaromatic phosphates selected from the group consisting of triphenyl phosphate and tricresyl phosphate, acyl triesters of glycerine wherein each acyl group contains 2-18 carbon atoms, and dialkyl alkyl phosphonates wherein each alkyl group contains 1-8 carbon atoms.

8. A composite article comprising at least two rigid elements adhered together by an in situ polymerized layer of an adhesive composition comprising monomeric alkyl tx-cyanoacrylate wherein the alkyl group contains 1-8 carbon atoms, and 1-20% by weight based on the weight of said a-cyanoacrylate of butyl cyanoacetate.

9. A composite article comprising at least two rigid elements adhered together by an in simpolymerized layer .of an adhesivecomposition comprising monomeric allcyl 'a-cyanoacrylate wherein the alkyl group contains 18 carbon atoms, and 1-20% byweight based on the weight ,a-cyanoacrylate wherein the alkyl group contains 1-8 elements adhered together by an in situ polymerized layer 2,i"84,1f8i' the weight of said a-cyanoacrylate of dimethyl succinate. 14.. Ac'omposite article comprising at least two rigid elements adhered together byan insitupolymerized layer of an adhesive composition comprising monomeric of said a-cyanoacrylate of dimethyl succinate. 5 vmethyl u-cyanoacrylate containing 1-5% by weight based 10. A composite article comprising at least two rigid on the weight of said a-cyanoacrylate of dimethyl seba elements adhered together by an in situ polymerized layer cate. of an adhesive composition comprising monomericalkyl References Cited in the file of this patent carbon atoms, and 120% by weight based on the weight 10 UNITED STATES PATENTS of said a-cyanoacrylate of dimethyl sebacate.

11' A com osite article com risin at least two ri id DAlelio June 1941 g 2,306,533 Frederickson Dec. 29, 1942 elements adhered together by an in situ polymerized layer 2,346,858 Mighton Apr. 18, 1944 of an adhesive composition comprising monomeric methyl i 2,467,927 Ardis Apr. 19, 1949 a-cyanoacrylate containing 145% by weight based on the .1 2 492 170 Mast et a1 Dec 27 1949 ;weight of said e-cyanoacrylate of butyl cyanoacetate.

. v p 2,535,827 Ardis et a1. Dec. 26, 1950 -12. A composite article comprising at-least two rigid 2 721 858 JO net et 31 Oct 25 1955 elementsadhered together by an in situ polymerized'layer y of an adhesive composition comprising monomeric methyl RBI PA NT wcyanoacrylate containing l-5% by weight based on the P F0 TE S weight of said m-cyanoacrylate of trici'esyl phosphate. Great Bmam 1948 13. A composite article comprising at least two rigid OTHER REFERENCES of an adhesive composition comprising monomeric methyl Synthetic 1944, P g

ot-cyan'oa'crylate containing 1-5% by weight based on 3 

1. A COMPOSITE ARTICLE COMPRISING AT LEAST TWO ELEMENTS ADHERED TOGETHER BY AN IN SITU POLYMERIZED LAYER OF AN ADHESIVE COMPOSITION COMPRISING MONOMERIC ACYANOACRYLATE ESTER OF THE FORMULA 